Effects of flavor salience on aversion performance following relatively long-delay backward conditioning procedures

Male albino rats (n = 144) received a 0.15 M injection of lithium chloride (at 2.0% body wt), followed 10, 30, or 75 min later by a 5.0% casein CS or a 10.0% sucrose CS, casein being the more salient CS. For each CS one-third of the rats received no fluid during the toxin-CS interval. The remaining two-thirds of the rats received 2-min access to distilled water or to a novel flavor 5 min after onset of the toxin-CS interval. For sucrose CS groups, the novel flavor was casein; for casein CS groups, the novel flavor was sucrose. Groups which received no fluid during the toxin-CS interval showed reliably greater aversion effects to the casein CS than to the sucrose CS. Results of Test Trial 1 showed that aversion to casein was relatively unchanged across toxin-CS intervals, while aversion to sucrose decreased reliably from the 10-min to the 30- and 75-min intervals. However, for each toxin-CS interval, aversion to the sucrose CS was reliably enhanced when casein access occurred in the interval, relative to that for distilled water or no fluid access. For the casein CS, access to sucrose or distilled water in the toxin-CS interval altered aversion effects, relative to the no fluid condition, depending on the interval.